Electronic whiteboards, in which a touch panel is provided on flat panel display equipment such as liquid crystal displays and plasma displays, or display equipment using a projector, are used. The electronic whiteboards are used in education, conferences in companies, and the like because such an electronic whiteboard is connectable to a personal computer (PC) and capable of displaying an enlarged image of an image supplied from the connected PC.
The electronic whiteboard also has a function, which makes use of its touch panel feature, of allowing a user to operate a PC which is supplying an image displayed on the electronic whiteboard by directly touching the displayed image. An interactive whiteboard application program that runs on a PC also comes with the electronic whiteboard. The interactive whiteboard application program causes a screen to serve as a whiteboard and enables a user to handwrite characters and the like on the screen using the touch panel feature, to capture an image supplied from a PC and handwriting on the captured image in an overlaying manner, and the like.
Concrete example products of such an interactive whiteboard include StarBoard (registered trademark) of Hitachi Solutions, Ltd. and Cyber Conference System (registered trademark) of Pioneer Cooperation.
When such an electronic whiteboard that enables a user to handwrite characters and the like and superimpose handwriting on a captured image is used in a conference, notes and the like can be directly written onto a screen of the electronic whiteboard where a material for presentation is displayed as appropriate. Recording a screen image inclusive of the added notes and the like as required is also enabled. Accordingly, because displayed screen images can be played back and reused at closing of the conference, it becomes possible to draw a conclusion and the like efficiently.
Meanwhile, as video input techniques develop, equipment that supports a plurality of types of video inputs including High-Definition Multimedia Interface (HDMI) and Video Graphics Array (VGA) has proliferated. Along with this proliferation, video input cables of various specifications have come to be supported. Electronic whiteboards also support a plurality of video inputs and are connectable with video input cables of various specifications. Accordingly, a user can connect a plurality of PCs to an electronic whiteboard and switch an image displayed on the electronic whiteboard among images that are supplied from the different PCs.
A technique relevant to this is disclosed in Japanese Patent Application Laid-open 2002-366343, for example. According to this technique, a plurality of computers are connected to an electronic whiteboard via a switcher; any one of the computers is selected; a video signal is supplied from the selected computer to the electronic whiteboard; control signals are exchanged between the selected computer and the electronic whiteboard.
To use such an electronic whiteboard having these functions in a conference, it is desirable that operating the electronic whiteboard, displaying necessary information thereon, and inputting necessary information thereto can be performed without hindering the progress of the conference. However, conventional electronic whiteboards are disadvantageous in that when a video signal that is supplied from a device connected to the electronic whiteboard to display a video is stopped or when an operation such as withdrawing a connection cable is performed, the video is not displayed on the electronic whiteboard any more, causing the screen undesirably to become blank. This undesirably hinders the progress of the conference because the screen becomes blank during the conference.
Therefore, there is a need for a method and an apparatus for enabling continuous image display on an electronic whiteboard, rather than causing the electronic whiteboard to go blank, even when a cable between the electronic whiteboard and a device from which a currently-displayed image is supplied is disconnected.